View Full Version : 7562 theory of operation

09-05-2007, 06:51 PM
I have a few questions to help me better understand the 7562. My understanding(right or wrong) is that when the 7562 "sees" engine rpm, the yellow wire feed solenoid goes active, without pwm. When boost is being controlled, does this stay full open, or does it pwm with the green feed wire solenoid?
I am having problems with controlling boost on the trans brake, but it seems to track boost down the track pretty well. At this point I will describe my installation, so if I have something wrong I can change it.
My wastegate "open" plumbing comes from my compressor housing. I have a 5pound spring in the wastegate. The spring side of the wastegate has an 18" long -4 teflon line to a "T" that both solenoids are directly attached to. On the inlet of the feed solenoid, I installed an orfice to limit flow. The feed solenoid is supplied by CO2 regulated to 45psi.
With no plumbing to the spring side of the wastegate(just vented) The car will make 5-6 psi on the trans brake. With the 7562 connected, it would make around 12psi, no matter how low I set the launch boost. After installing the orfice at the inlet of the feed solenoid, the trans brake boost is lower(around 10 psi).
My pwm traces show saturation on the transbrake.
I'll attach one trace from the track(before installing the orfice) and one from the driveway with the orfice.

09-09-2007, 03:32 PM
I've changed the location of the solenoids. They are mounted directly to the wastegate(spring side) now. Before mounting them, I did a short log on the trans brake, so the spring side of the regulator was just vented to atmosphere. This would be the boost pressure I would expect to see when the vent solenoid is open... Correct? What I dont understand is, in this condition(no soleniods connected) the engine wont be able to achieve the desired boost- so why isn't the pwm staying on the low(40) end of the scale?
After hooking up the solenoids, my next log would show a spike of around 10 psi, then it slowly went to the minimum I've yet seen (about 7-8psi). Again I dont see the pwm staying higher to try to vent the wastegate to the desired pressure.

09-25-2007, 08:50 AM

Please send me your phone number to msdtech@msdignition.com so I can call you.


MSD tech4